This invention relates to a high-speed, melt-spinning process for producing self-crimpable, nylon 66 carpet yarn and to the yarn produced thereby.
The term "high-speed", as used herein, means a speed of at least 2300 meters per minute (mpm).
The term "self-crimpable" yarn, as used herein, means a yarn which when subjected to 180.C. dry heat for five minutes while under no tension develops a helical crimp.
The term "carpet yarn", as used herein, means a yarn having an elongation-to-break (E.sub.b) of less than 120%, a total denier of at least 750 and an average denier per filament (dpf) of at least 13.
The term nylon 66, as used, means a fiber-forming polymer consisting essentially of repeating units of the formula: ##STR1## It is understood that the polymer may contain minor amounts of additives such as dye adjuvants, delustrants, stabilizers, and the like commonly employed in the art.
Nylon 66 carpet yarn having good luster is conventionally produced by low-speed, melt-spinning processes in which molten nylon 66 is extruded through orifices of a spinneret to form molten streams that are quenched (solidified) by means of a cross-flow of air in a quenching chamber, commonly referred to as a chimney, to form filaments that are converged on a guide to provide an as-spun yarn. A liquid finish is then applied to the yarn and the yarn is either collected at a speed of 400 to 800 mpm and subsequently drawn several times (e.g. 3.5 times) its length in a separate operation or drawn in-line before being collected. The drawn yarn is then crimped by conventional means, for example, by air-jet texturing, gear-crimping, or stuffer box crimping, either in-line during the melt-spinning process or subsequent thereto in a separate operation. It would be economically desirable to provide a high-speed, melt-spinning process for producing a self-crimpable, monocomponent nylon 66 carpet yarn having good luster in which the extra drawing and crimping steps are eliminated.
U.S. Pat. No. 2,957,747 describes a melt spinning process for producing self-crimpable nylon 66 apparel yarn in which high spinning speeds are utilized. However, when one attempts to use high spinning speeds in conventional melt spinning processes to produce nylon carpet yarn which has a large number of large denier filaments, several problems are encountered. One problem encountered is that the filaments are whipped about in the chimney to a much greater extent and the likelihood that molten streams will come into contact with and stick (fuse) to one another in the chimney is greatly increased. Another problem is that the larger denier filaments simply do not cool sufficiently to prevent filaments from sticking to one another on the convergence guide. Fused filaments ultimately lead to broken filaments which cause wraps and other processing difficulties, particularly in cabling operations. Broken filaments also can distract from the aesthetics of the yarn and carpets made therefrom. Also, if the level of fused and/or broken filaments becomes too high during melt-spinning, the yarn cannot be collected in an orderly fashion.
Yet another problem encountered is that conventional nylon 66 carpet yarn spun at high speeds has low (poor) luster, i.e. is dull.
U.S. Pat. No. 4,238,439 describes a high-speed, meltspinning process for producing self-crimpable carpet yarn utilizing a nylon 66 copolymer. However, carpet yarn described therein does not have good luster and requires the use of a copolymer which is more complicated to make than nylon 66.